In reply to Euge: I did try the Velum jacket on at the same time as I got the Asgard and I think sizing was similar. I wouldn't say they were 'really' tight fitting, but certainly a bit slimmer than most other brands. I tried on various jackets from Rab/North Face/Montane at the time, and generally in those brands I could just about have fitted into a medium with thin layers, except that the arms were too short, so I would have bought an L in those. The Berghaus in M was just slightly too tight across the chest, so I went with the L.
I have always bought jackets in 40. I'm maybe a 39.5-40.5 in reality. I tend to buy t-shirts in M, and jumpers in M/L. I tried the Asgard on again just now to try and get an idea of sizing. I'm wearing a t-shirt and a thin wool jumper, I could probably get a fleece/thin softshell on as well, but not much more than that. I do have quite wide shoulders though, so maybe a 42" chest with more normal shoulders and thin layers would work in an L. Best to try on I guess. Or order both sizes and send one back?
You've probably found this already, but SportPursuit are selling off Berghaus stuff really cheap for the next couple of days, including the Asgard and Velum. I've used them before and they're fine, just be aware that they dont send orders out until a few weeks after the sale ends, but I'm pretty sure they tell you that before you order anyway. Its sportpursuit.com or if you sign up via this link then I'll get a £5 credit if you do buy something.
http://www.sportpursuit.com/join/Paul_Leader-Williams_58551